1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD device which facilitates to improve picture quality of two-dimensional (2D) and three-dimensional (3D) images by automatically converting an image driving mode (2D/3D) in accordance with a viewing distance, and a method for driving the same.
2. Discussion of the Related Art
A display device has been continuously developed to satisfy various requirements such as large-sized screen and thin profile. Especially, there is the explosive increase for flat type display devices having advantages of thin profile, lightness in weight, and low power consumption.
The flat type display device may include a liquid crystal display device (LCD), a plasma display panel (PDP), a field emission display device (FED), a light-emitting diode display device (LED), and etc.
Among the various flat panel display devices, the LCD device is widely used owing to various advantages, for example, technical development for the mass production, easiness of driving means, low power consumption, and high-quality resolution.
The LCD device comprises a liquid crystal panel with a plurality of liquid crystal cells arranged in a matrix configuration; a backlight unit for supplying light to the liquid crystal panel; and a driving circuit for driving the liquid crystal panel.
There are the plural liquid crystal cells defined by crossing a plurality of gate lines and a plurality of data lines of the liquid crystal panel. Each liquid crystal cell is provided with pixel electrode and common electrode for applying an electric field. Each of the liquid crystal cells is switched via a thin film transistor (TFT).
The driving circuit includes a gate driver (G-IC) for supplying a scan signal to the gate lines; a data driver (D-IC) for supplying a data voltage based on an image signal to the data lines; a timing controller (T-con) for supplying a control signal to the gate driver and data driver, and supplying image data to the data driver; and a light source (backlight) for supplying light to the liquid crystal panel.
In the LCD device, an alignment of liquid crystal is changed depending on a voltage formed between the pixel electrode and the common electrode pixel-by-pixel. Thus, transmittance of light emitted from the backlight unit can be controlled through the alignment of liquid crystal, to thereby display the image.
Recently, a user's demand for a stereoscopic image is rapidly increased so that an LCD device capable of displaying 3D (3-dimensional) image as well as 2D (2-dimensional) image is actively developed.
The LCD device displaying 3D image can realize the 3D image through a difference in viewing between both eyes of the user (binocular parallax display).
There have been proposed a shutter glass method using stereoscopic glasses, and a patterned retarder method using polarizing glasses.
FIG. 1 illustrates a method of realizing 3D image by the use of shutter glass according to the related art.
Referring to FIG. 1, the method of realizing 3D image by the use of shutter glass according to the related art is to use the user's binocular parallax.
After 2D left-eye image and 2D right-eye image, which are different from each other, are respectively viewed by the left and right eyes of the user, two of the 2D images are integrated so that the integrated image is recognized as the 3D image by the user.
For this, a liquid crystal panel 10 separately displays 2D images for the left-eye viewing and right-eye viewing with a difference in time. Through the use of shutter glass 20, the right-eye viewing is intercepted and the 2D image is viewed by the left eye when the 2D image for the left-eye viewing is displayed on the liquid crystal panel 10; and the left-eye viewing is intercepted and the 2D image is viewed by the right eye when the 2D image for the right-eye viewing is displayed on the liquid crystal panel 10.
Thus, after the different 2D images are respectively viewed by the left eye and the right eye with the different in time, the viewed 2D images are integrated so that the integrated image is recognized as the 3D image by the user.
FIG. 2 illustrates a method of realizing 3D image by the use of polarizing glasses according to the related art.
Referring to FIG. 2, the patterned retarder method using the polarizing glasses provides a patterned retarder (PR) layer in a liquid crystal panel 10. Light emitted from the liquid crystal panel 10 is leftward or rightward circularly polarized by the patterned retarder (PR) layer.
At this time, the left-eye image is displayed in pixels corresponding to the half of the pixels included in the liquid crystal panel 10, for example, the pixels in the odd-numbered lines of the liquid crystal panel 10; and the right-eye image is displayed in pixels corresponding to the other half of the pixel included in the liquid crystal panel 10, for example, the pixels in the even-numbered lines of the liquid crystal panel 10.
The patterned retarder (PR) layer leftward circularly retards the light emitted from the half of the pixels included in the liquid crystal panel 10, to thereby display the left-eye image. Also, the patterned retarder (PR) layer rightward circularly retards the light emitted from the other half of the pixels included in the liquid crystal panel 10, to thereby display the right-eye image.
The left-eye image is perceived only by the user's left eye through the left glass of the polarizing glasses 30; and the right-eye image is perceived only by the user's right eye through the right glass of the polarizing glasses 30.
Thus, the left-eye image and the right-eye image are separately displayed, and then two of the left-eye image and the right-eye image are integrated, whereby the integrated image is recognized as the 3D image by the user.
FIG. 3 illustrates an image distortion when the 3D image is displayed on the LCD device according to the related art. FIG. 4 illustrates user's fatigue occurrence when the 3D image is displayed on the LCD device according to the related art.
Referring to FIGS. 3 and 4, in case of the aforementioned shutter glass method and patterned retarder method, the picture quality of 3D image is affected by the viewing distance.
As shown in FIG. 3, if the user watches the image 40 displayed on the liquid crystal panel 10 at an appropriate distance, the image transmitted via the shutter glass 20 or polarizing glass 30 is recognized as the normal 3D image.
However, if the user watches the image 40 displayed on the liquid crystal panel 10 at a distance shorter than the appropriate distance, the image transmitted via the shutter glass 20 or polarizing glass 30 is distorted, which causes the deteriorated picture quality of 3D image.
As shown in FIG. 4, when the user watches the 3D image displayed on the liquid crystal panel 10, the user's visual fatigue may be changed depending on the viewing distance. When the user watches the 3D image, the user's visual fatigue can be reduced by the appropriate viewing distance.
For example, if the user watches the 3D image while maintaining the appropriate distance above 2 m (more preferably about 2.4 m) from the liquid crystal panel 10, the user does not feel fatigued with the 3D image having +1 m˜−4 m image depth.
However, if the user watches the 3D image while maintaining the distance less than 2 m from the liquid crystal panel 10, the user feels fatigued with the 3D image. Thus, when the user watches the 3D image at the short distance from the liquid crystal panel 10 for a long time, it might make the user dizzy.